The present invention provides viral agents that have application in the treatment of neoplasms such as tumours, particularly tumours derived from colon cells, more particularly liver tumours that are metastases of colon cell primary tumours. Still more particularly are provided replication efficient adenovirus constructs that selectively replicate in response to transcription activators present in tumour cells, these factors being present either exclusively or at elevated levels in tumour cells as compared to other cells, and thus which lead to tumour cell death and cell lysis.
By injecting these viral agents locally into the liver it is possible to treat liver metastases; which are a major cause of morbidity in colon cancer patients. Applications beyond this, e.g. to other sites and other tumours, such as colorectal cancers and melanomas, are also provided.
Colon cancer presents with locally advanced or metastatic disease in the majority of patients. Most patients are left with liver metastases as the only site of disease after resection of the primary tumour. Partial liver resection only cures about 10% of patients, while in patients with multiple metastases in both liver lobes resection is not feasible and loco-regional or systemic treatment with chemotherapy is indicated (Labianca et al., 1997). Systemic chemotherapy with 5-fluorouracil and leucovorin or irinotecan will produce response rates of only 20% (Cunningham et al., 1998; Stupp et al., 1998).
Locoregional chemotherapy of the liver has been explored for over 15 years. Most liver metastases are supplied with blood by the hepatic artery, so intra-arterial hepatic chemotherapy (IAHC) allows for much higher exposure of the metastases to cytotoxic drugs. The high extraction rate of normal liver decreases the systemic drug concentration resulting in less toxicity with IAHC having been shown repeatedly to give response rates over 60% (Kemeny et al., 1987; Kemeny et al., 1992; Patt and Mavligit, 1991).
Specific defects in tumour cells make it possible to devise rational strategies for targeting tumour cells without harming normal cells. With the exception of anti-angiogenic therapy, this usually requires introduction of exogenous DNA into tumour cells, and the most efficient way to do this is with viruses. For example, U.S. Pat. No. 5,698,443 describes a tumour specific adenovirus that is targeted at prostate cancer cells. This virus utilises a prostate specific enhancer sequence driving the viral E1 genes and the patent suggests its use to express toxins specifically in the target cell.
Viruses which replicate selectively in tumour cells have great potential for gene therapy for cancer. In principle, selectively replicating cytotoxic viruses can spread progressively through a tumour until all of its cells are destroyed. This overcomes the need to infect all tumour cells at the time the virus is injected, which is a major limitation to conventional replacement gene therapy, because in principle virus goes on being produced, lysing cells on release of new virus, until no tumour cells remain. An important fundamental distinction in cancer gene therapy is thus between single hit approaches, using non-replicating viruses, and multiple hit approaches, using replicating viruses.
Single hit approaches work by directly transducing tumour cells with toxic genes; ignoring bystander effects, one virus particle kills one cell. Examples include restoration of tumour suppressor gene expression and conditional expression of toxins using tumour-specific promoters. For single hit approaches the amount of virus injected is an important limiting factor. Multiple hit approaches circumvent this limitation either by provoking an immune reaction against tumour cells, or by using viruses that replicate within the tumour. Since the majority of tumour cells are not killed by the injected virus itself, the amount of virus injected should not be an important factor limiting the therapeutic response.
Classic gene replacement therapy has been performed with retroviruses expressing p53 (Roth et al., 1996). Since p53 can be converted to its oncogenic form by mutations at over 500 sites in the open reading frame (Flaman et al., 1994), retroviral replication will convert at least 1% of the transduced p53 to such undesired mutant form. This means that each patient received around 25 million infectious units of virus expressing mutant p53 (Estreicher and Iggo, 1996).
A more promising approach expressing wild type p53 using an adenovirus, Ad-CMV-p53, has been demonstrated clinically in head and neck cancer and is currently under investigation in lung, colon and liver cancer (Clayman et al., 1998). Adenoviruses are relatively stable, can be produced at high titres, and can infect both quiescent and dividing cells of many different types. Overall, Ad-CMV-p53 appears exceptionally non-toxic but probably ineffective as a single agent; hence, there is a place for more aggressive second generation viruses.
Further target specific defects are mutations of p16, cdk4, cyclin D or Rb (Bartek et al., 1997) in the retinoblastoma pathway which cause loss of G1/S control and essentially all tumours have these. The only significant exception is colon cancer, where mutations in the Rb pathway itself are rare. The net result of these defects is increased E2F activity, which means that tumours can be selectively targeted by viruses expressing toxic genes from E2F-regulated promoters. This has been demonstrated using an adenovirus expressing the HSV thymidine kinase gene from such a promoter (Parr et al., 1997); cells containing Rb-pathway mutations express tk and can be killed by ganciclovir. Such an approach relies on an increase in the activity of specific transcription factors in tumour cells.
The rational basis for tumour targeting is better understood for non-replicating E2F-targeting viruses than it is for p53, but both are still single hit approaches and it is very difficult to see how they can ever be used for more than treatment of local disease. The tumour burden in late stage disease is around 1012 cells, so while at an effective multiplicity of infection of one treatment would be feasible, in practice biodistribution and receptor problems mean that many orders of magnitude higher multiplicities are required.
One elegant way to circumvent this limitation is to recruit the immune system to kill the tumour cells. The role of the gene therapy virus is simply to provoke or reinforce the immune response. There is abundant evidence that tumours express new antigens, but in cancer patients the immune system has clearly failed to prevent tumour formation. Many currently attempted techniques target single antigens, eg production of cytotoxic T cells against MAGE antigens in melanoma, but the goal for therapy must be to induce a simultaneous response against multiple different antigens, because genetic instability in tumours means targeting of single antigens is unlikely to produce lasting responses because the number of tumour cells exceeds the mutation rate. Hence acquired resistance to immunotherapy is common.
An attractive solution to the single hit problem is to produce virus within the tumour. This can be achieved by injecting retroviral producer cell lines into the tumour bed, a strategy currently being tested in a clinical trial for glioblastoma (reviewed by Roth and Cristiano, 1997). This is an elegant but limited approach as it relies on immune privilege in the CNS to avoid immediate rejection of the grafted cells, and tumour targeting depends on the fact that retroviruses do not infect non-dividing normal brain cells. It falls short of the goal of tumour cell-specific viral replication because the viruses produced are not themselves replication competent and virus production is dependent on survival of the packaging cells rather than the presence of tumour cells.
The prototype tumour selective virus is a defective adenovirus lacking the E1B 55K gene (d1 1520ONYX 015, Bischoff et al., 1996). In normal adenoviruses 55K inactivates p53, hence it should not be required in cells where p53 is mutant. In practice, many cells containing wild type p53 are killed by the virus (Heise et al., 1997). The present inventors have tested this in H1299 p53-null lung carcinoma cells containing wild type p53 under a tetracycline-regulated promoter and found that dl 1520 replicates as well in the presence as in the absence of wild type p53. Besides targeting p53, E1B 55K is required for selective viral RNA export (Shenk, 1996) and it is not immediately obvious how loss of p53 could substitute for this function. At present there is no convincing evidence that dl 1520 targets p53 defects (Goodrum 1997, Goodrum 1998, Hall 1998, Rothman 1998, Turnell 1999).
As with p53-expressing viruses, combination therapy with chemotherapy and d1 1520 gives better results both in vitro and in xenografts (Heise et al., 1997). In principle, the virus should undergo multiple rounds of replication until there are no tumour cells remaining and since each infected cell produces 103 to 104 new virus particles, the amount of input virus should not be limiting. In practice, the required amount of d1 1520 virus injected is comparable for therapy with Ad-CMV-p53. This means that the virus is not performing as expected for a replicating virus with the reasons for this again probably quite complex. Adenoviruses normally produce superficial mucosal infections which are spread by droplets containing infected cells. Infected cells retain progeny virus. Lack of effective virus release from lysed cells will militate against the production of deep, spreading infection, which is the goal if virus is to penetrate to all parts of the tumour.
Rational targeting of E2F defects is complicated by the fact that as part of its life cycle the adenovirus already produces proteins (E1A and E4 orf 6/7) which target E2F. Since E1A and orf 6/7 are multifunctional proteins the effect of E1A and orf 6/7 mutations is complex and unpredictable.
In addition to E2F and p53, there are four transcription factors whose activity is known to increase in tumours. They are Tcf4, RBPJxcexa and Gli-1, representing the endpoints of the wnt, notch and hedgehog signal transduction pathways (Dahmane et al., 1997; Jarriault et al., 1995; van de Wetering et al., 1997) and HIF1 alpha, which is stabilised by mutations in the Von Hippel Lindau tumour suppressor gene (Maxwell et al 1999). Mutations in APC or xcex2-catenin are universal defects in colon cancer (Korinek et al., 1997; Morin et al., 1997); but they also occur at lower frequency in other tumours, such as melanoma (Rubinfeld et al., 1997). Such mutations lead to increased Tcf activity in affected cells. The hedgehog pathway is activated by mutations in the patched and smoothened proteins in basal cell cancer (Stone et al., 1996; Xie et al., 1998). Notch mutations occur in some leukaemias (Ellisen et al., 1991). Telomerase activation is one of the hallmarks of cancer (Hanahan D. and Weinberg RA. The hallmarks of cancer. Cell. 100, 57-70, 2000) and results from increased activity of the telomerase promoter, although the mechanism is unknown. According to Cong Y S et al (1999, HMG 8, 137-42) the elements responsible for promoter activity are contained within a region extending from 330 bp upstream of the ATG to the second exon of the gene and thus this sequence is a further suitable promoter sequence for use in the viral constructs and viruses of the invention.
The present inventors have now designed and produced viral DNA constructs, and replicating viruses encoded thereby, preferably in the form of recombinant viral constructs and viruses, which rationally target known causal oncogenic transcription defects in tumours by using these to control transcription of one or more early viral genes encoding for proteins which are mechanistically directly involved in viral nucleic acid replication (for examples of such genes see eg. DePamphilis, M L, Concepts in Eukaryotic DNA Replication pp 481-484 and 488-491, 1999 Cold Spring Harbor Laboratory Press, New York which is incorporated herein by reference). Preferably these viral genes are selected from the group consisting of polymerase, primase, nuclease, helicase, ligase, terminal protein and nucleic acid binding protein genes. Preferred enzymatic products of five of these genes are classified in the following Enzyme Commission classifications: polymerase (EC 2.7.7.7), primase (EC 2.7.7.6), nuclease (EC 3.1.11-25), helicase (EC 3.6.1.3) and ligase (EC 6.5.1.1-2). These classifications may vary, for example, in parvoviruses, eg. Adenoassociatedviruses (AAV), they include NS1/Rep proteins, which have nuclease and helicase activities essential for replication In the preferred constructs and viruses produced by the inventors these genes are particularly the viral DNA polymerase, viral DNA terminal protein and/or viral DNA binding protein genes. Preferred viruses are those having E1, E2 and E3 viral transcription units, such as adenoviruses. It is particularly preferred that at least the E2 transcription unit of the virus is altered such that it is made responsive to factors that are present at increased levels or increased activity, or are only present in, a target tumour cell. Rittner et al (J. Virol (1997) p 3307-3311) teach that it is not possible to manipulate the E2 promoters close to the cap sites because of the overlap with the major late open reading frame L4. The present inventors however find that this manipulation is indeed possible with advantageous results.
It has thus been determined that by controlling nucleic acid replication capability, rather than factors such as RNA export capability or toxicity due to insertion of recombinant genes, the inventors can provide selectivity of cytotoxic effect to tumour cells.
Most importantly and advantageously, the present inventors have made possible to target tumour cells with a virus encoding only wild type viral proteins, whose expression is specifically regulated by transcription factors preferentially or exclusively activated in tumour cells. Preferred virus encodes a full set of wild type proteins. Such virus can be used to better effect than prior art viral agents which have relied on mutation of viral proteins or targeting of cells of a particular tissue origin, eg. prostate.
Thus in a first aspect of the present invention there is provided a viral DNA construct encoding for a virus that is capable of replication in a human or animal tumour cell type and causing tumour cells of that type to die characterised in that the construct comprises one or more selected transcription factor binding sites together with, and operatively positioned such as to promote expression of, open reading frames encoding early viral proteins, the protein products of those reading frames being mechanistically directly involved in viral construct nucleic acid replication wherein the selected transcription factor binding sites are for a transcription factor the level or activity of which is increased in a human or animal tumour cell relative to that of a normal human or animal cell of the same type.
Preferred constructs of the invention have a nucleic acid sequence corresponding to that of a wild type virus sequence characterised in that it has one or more wild type transcription factor binding sites replaced by one or more selected transcription factor binding sites, these sites being operatively positioned in the promoter region which controls expression of early genes such as to promote expression of the open reading frame of the gene, the protein products of those genes being mechanistically directly involved in viral nucleic acid replication
wherein the selected transcription factor binding sites are for a transcription factor the level or activity of which is increased in a human or animal tumour cell relative to that of a normal human or animal cell of the same type.
Preferably the viral DNA construct is characterised in that the sites which replace the wild type transcription factor sites controlling expression of said early genes are for a transcription factor whose activity or level is specifically increased by causal oncogenic mutations.
While the controlled open reading frames or genes may be one or more of the viral polymerase, primase, nuclease, helicase and ligase, preferably they are one or more of the DNA polymerase, DNA terminal protein and/or DNA binding protein. More preferably the construct or virus is such that it has E1, E2 and E3 regions and the tumour specific transcription factor binding site replaces one or more wild type E2 transcription factor binding sites.
Preferably the viral DNA construct is characterised in that it encodes a functional viral RNA export capacity. For adenovirus this is encoded in the E1 and E4 regions, particularly the E1B 55K and E4 orf 6 genes. Thus preferably the encoded virus is of wild type with respect to expression of these genes in tumour cells. Most preferably the E1B 55K and E4 orf 6 open reading frames are functional and/or intact where present in the corresponding wild type virus.
It will be realised by those skilled in the art that any virus which is potentially cytotoxic to tumour cells may be employed in producing viral constructs of the present invention. Particularly examples may include adenovirus, lentivirus, polyoma virus, vaccinia virus, herpesvirus and parvovirus. Preferably the virus is an adenovirus, more preferably an adenovirus that is of high specificity for a target tumour cell type, eg. for a colon tumour type.
Preferred colon tumour specific adenoviruses are encoded by viral DNA constructs corresponding to the DNA sequence of Ad5 or one or more of the enteric adenoviruses Ad40 and Ad41 modified as described above. Ad40 and Ad41, which are available from ATCC, are selective for colon cells and one important difference to Ad5 is that there is an additional fibre protein. The fibre protein binds to the cell surface receptor, called the coxsackie-adeno receptor or CAR for Ad5. Colon cells have less CAR than lung cells which Ad5 is adapted to infect. Ad40 and Ad41 have two fibre proteins, with the possibility being that they may use two different receptors. The expected form of resistance to virus therapy is loss of the receptor, which obviously prevents infection. Genetic instability in tumours means this will happen at some reasonable frequency; about 1 in 100 million cells, a mutation rate of 1 in 108. If you have to delete two receptors you multiply the probabilities; ie. loss of both will occur in 1 in 1016 cells. A tumour contains between 109 and 1012 cells. Hence resistance is less likely to develop if a virus uses more than one receptor. One fibre protein in Ad40 and 41 uses CAR whilst the receptor used by the other is as yet unknown.
Advantageously the use of the constructs of the invention, particularly in the form of viruses encoded thereby, to treat liver metastasis is relatively non-toxic compared to chemotherapy, providing good spread of virus within the liver aided by effective replication.
Preferred viral constructs of the invention are derived from adenovirus or parvovirus genomic DNA, more preferably adenovirus genomic DNA, and are mutated such that transcription of essential viral genes encoded by the E2 viral transcription unit is made dependent on the presence of oncogenic mutations in tumour cells. Preferably only cells containing these oncogenic mutations can activate transcription of the viral E2 genes. Since the E2 unit encodes the viral DNA polymerase, DNA terminal protein and DNA binding protein, the virus can only replicate in tumour cells. It is preferred that the E2 early promoter transcription factor binding site is replaced by the tumour cell specific transcription factor binding site.
Preferred tumour specific transcription factor binding sites that are used in place of wild type sites are those described above as Tcf-4, HIF1alpha, RBPJxcexa and Gli-1 sites, and a fragment of the telomerase promoter conferring tumour-specific transcription. A most preferred transcription factor binding site is that which binds Tcf-4, such as described by Vogelstein et al in U.S. Pat. No. 5,851,775 and is responsive to the heterodimeric xcex2-catenin/Tcf-4 transcription factor. As such the transciption factor binding site increases transcription of genes in response to increased xcex2-catenin levels caused by APC or xcex2-catenin mutations. The telomerase promoter is described by Wu K J. et al (1999, Nat Genet 21, 220-4) and Cong Y S. et al (1999 HumMol Genet 8, 137-42). A further preferred binding site is that of HIF1alpha, as described by Maxwell P H. et al, (1999 Nature 399, 271-5). One may use a HIF1alpha-regulated virus to target the hypoxic regions of tumours, involving no mutation of the pathway as this is the normal physiological response to hypoxia, or the same virus may be used to target cells with VHL mutations either in the familial VHL cancer syndrome, or in sporadic renal cell carcinomas, which also have VHL mutations. A retrovirus using the HIF promoter to target hypoxia in ischemia has already been described by Boast K. et al (1999 Hum Gene Ther 10, 2197-208).
Particularly the inventors have now provided viral DNA constructs, and viruses encoded thereby, which contain the Tcf transcription factor binding sites referred to above in operational relationship with the early gene open reading frames described above, particularly in place of wild type transcription factor binding sites in the E2 promoter and shown that these are selective for tumour cells containing oncogenic APC and xcex2-catenin mutations. Tcf-4 and its heterodimer bind to a site designated Tcf herein. Preferred such replacement sites are single or multiples of the Tcf binding sequence, eg. containing 2 to 20, more preferably 2 to 6, most conveniently, 2, 3 or 4 Tcf sites.
Particular Tcf sites are of consensus sequence (A/T)(A/T)CAA(A/T)GG, see Roose, J., and Clevers, H. (1999 Biochim Biophys Acta 1424, M23-37), but are more preferably as shown in the examples herein.
More preferred viral constructs and viruses of the invention are those having E3 domains and are characterised in that they have mutations to one or more residues in the NF1, NFxcexaB, AP1 and/or ATF regions of the E3 promoter, more preferably those mutations which reduce E2 gene transcription caused by E3 promoter activity. The present inventors have particularly provided silent mutations, these being such as not to alter the predicted protein sequence of any viral protein, which alter the activity of key viral promoters.
NFxcexaB is strongly induced in regenerating liver cells, ie. hepatocytes (see Brenner et al J. Clin. Invest. 101 p802-811). Liver regeneration to fill the space vacated by the tumour is likely to occur following successful treatment of metastases. In addition, if one wishes to treat hepatoma, which arise on a background of dividing normal liver cells, then destroying the NFxcexaB site is potentially advantageous.
In a preferred embodiment of the first aspect of the present invention the inventors have replaced a short region in the E2 early promoter, which is not overlapped by coding sequence, with multiple Tcf binding sites, more preferably 3 or 4 such sites, and most preferably 4 sites. One resulting preferred viral construct and encoded virus are referred to herein as Ad-Tcf3, having 3 such sites, and the virus expresses E2 gene products and replicates better in colon than in lung tumour cells (see Examples). This shows that mutations of the type described can modify the activity of the E2 promoter in the desired way without untoward effects on other aspects of the viral life cycle. This is not obvious a priori because, as well as encoding the E2 promoter, this region is transcribed and retained in the 5xe2x80x2-untranslated region of the pVIII protein RNA, it is transcribed but spliced out of the L5 late RNA and it forms part of the 3xe2x80x2-untranslated region of the 33k protein RNA.
Although Ad-Tcf3 replicates better in colon than lung tumour cells, the difference is only around ten-fold. LGC, a virus of the invention combining the E2 mutations in Ad-Tcf with an E1B 55K deletion, shows around 1000-fold selectivity for colon cancer cells. This demonstrates that E2 promoter activity can be made limiting for viral replication, because the identical virus with the normal E2 promoter (LGM) shows no specificity for colon cells. For a colon-targeting strategy this is an important result because it means a colon-specific virus can be made by titrating the E2 promoter activity.
The probable explanation for the selectivity of LGC is that the E1B 55k protein is required for nuclear export of late viral RNAs, including the E2 DBP late RNA, and that the E2 RNA export defect in E1B 55K-deficient viruses can be overcome by increasing E2 RNA production by inserting Tcf sites in place of the normal transcription factor binding sites in the E2 promoter.
One method for increasing the specificity of the AdTcf3, and similar 3xTcf driven E2 viruses of the invention for colon tumours is to reduce its E2 promoter activity in non-colon cells. One possible way to do this is to alter the number of Tcf sites. Reduction in the number of Tcf sites to two could reduce non-specific leakiness, but since Tcf promoters are actively repressed in non-colon cells by groucho (Fisher and Caudy, 1998) and acetylation (Waltzer 1998) it is more likely that increasing the sites will give a more tightly regulated promoter as the more sites there are the more repressor will be bound in non-colon cells. E1A normally activates the E2 promoter through the ATF site. In the absence of such targeting E1A represses promoters, eg. by chelating p300/CBP. Since the ATF site is deleted in the Tcf-mutant E2 promoter, E1A produced by the virus should reduce general leakiness of the mutant E2 promoter in all cell types. The E3 promoter is back-to-back with the E2 promoter and the distinction between them is defined but functionally arbitrary. Hence further reduction of the activity of the mutant E2 promoter is possible by modifying or deleting transcription factor binding sites in the E3-promoter. Since the E3 promoter lies in coding sequence it cannot just be deleted. Instead the inventors have provided up to 16 silent substitutions changing critical residues in known NF1, NFxcexaB, AP1 and ATF sites (Hurst and Jones, 1987, Genes Dev 1, 1132-46, incorporated herein by reference).
Further viral constructs of the present invention may be provided by modifying the E2-late promoter of adenoviruses. The E2-early promoter controls transcription of DNA polymerase (pol), DNA binding protein (DBP) and preterminal protein (pTP). By mutating the E2 late promoter it is possible to have a similar effect, ie. at least in part, to the E1B deletion because E1B deletion reduces export of DBP RNA expressed from the E2 late promoter. DBP is required stoichiometrically for DNA replication, so reducing DBP production in normal cells is desirable. Since the E2 late promoter lies in 100k protein coding sequence it cannot just be deleted. Instead the inventors have determined that it can inactivated with silent mutations changing critical residues in known transcription factor binding sites.
Particular transcription factor binding sites in the E2 late promoter were identified by DNase I footprinting (marked I-IV in FIG. 4 herein; Goding et al, 1987, NAR 15, 7761-7780). The most important is a CCAAT box lying in footprint II. Mutation of this CCAAT box reduces E2 late promoter activity 100-fold in CAT assays (Bhat et al, 1987, EMBO J, 6,2045-2052). One such mutation changes the marked CCAAT box sequence GAC CAA TCC to GAT CAG TCC. (see FIG. 4 below). This is designed to abolish binding of CCAAT box binding factors without changing the 100k protein sequence. Additional silent mutations in the other footprints can be used to reduce activity further.
An alternative or additional mutation possible is to regulate expression of E1B transcription by mutating the E1B promoter. This has been shown to reduce virus replication using a virus in which a prostate-specific promoter was used to regulate E1B transcription (Yu, D. C., et al 1999 Cancer Research 59, 1498-504). A further advantage of regulating E1B 55K expression in a tumour-specific manner would be that the risk of inflammatory damage to normal tissue would be reduced (Ginsberg, H. S., et al 199 PNAS 96, 10409-11). The inventors have produced viruses with Tcf sites replacing the E1B promoter Sp1 site to test this proposition.
Further embodiments include the following possible modifications. To further restrict replication one can insert further tumour specific, eg. Tcf, sites in the E1A promoter. To achieve regulation by inserting short oligonucleotides, one must delete the existing regulatory sequences in the E1A promoter. This requires simultaneous mutation of both inverted terminal repeats and transfer of the packaging signal elsewhere, eg. to the E4 region. In contrast with, for example, the Calydon viruses, the design of the present inventors viruses means that, despite retaining a full complement of adenoviral genes, spare packaging capacity is available, which can be used to express conditional toxins, such as the prodrug-activating enzyme HSV thymidine kinase (tk). This could be expressed for example from the E3 promoter, whose activity is regulated in some of the viruses, to provide an additional level of tumour targeting. Alternatively, it could be expressed from a constitutive promoter to act as a safety feature, since ganciclovir would then be able to kill the virus. Constitutive tk expression in an E1B-deficient virus also increases the tumour killing effect, albeit at the expense of replication (Wildner, O., et al 1999 Gene Therapy 6, 57-62). An alternative prodrug-activating enzyme to express would be cytosine deaminase (Crystal, R. G., et al 1997 Hum Gene Ther 8, 985-1001), which converts 5FC to 5FU. This has advantage because 5FU is one of the few drugs active on liver metastases, the intended therapeutic target, but produces biliary sclerosis in some patients.
The amino-terminus of E1A contains a region of E1A that binds p300, a histone acetylase which functions as a general transcription factor. One way E1A activates genes is by bringing p300 to the promoter. To do this E1A binds transcription factors like ATF. Hence E1A activates promoters that contain ATF sites. Virus vMB13 herein retains the ATF site in the E3 promoter providing advantage in this respect. The problem is that if a promoter does not have an ATF site, E1A will repress it by binding p300. This is what happens with p53, for example: E1A blocks p53-dependent transcription in a manner that requires the p300 binding site in E1A. Tcf repression by E1A is a possibility in some cell lines, so mutation of the E1A p300-binding site may be preferred for such treatment.
The present inventors see a difference between vMB13 and vMB14 in HCT 116 cells, where the only difference between the two viruses is in the ATF site in the E3 promoter. Thus mutation of the E1A p300-binding site in vMB14 might be advantageous. Alternatively, the difference could be due to direct activation of the ATF site because Xu L et al (2000, Genes Dev 14, 585-595) report that ATF/CREB sites can be activated by wnt signals, although the mechanism is unknown.
Having produced a virus with one or more levels of regulation to prevent or terminate replication in normal cells, it is further preferred and advantageous to improve the efficiency of infection at the level of receptor binding. The normal cellular receptor for adenovirus, CAR, is poorly expressed on some colon tumour cells. Addition of a number of lysine residues, eg 15 to 25, more preferably about 20, to the end of the adeno fibre protein (the natural CAR ligand) allows the virus to use heparin sulphate glycoproteins as receptor, resulting in more efficient infection of a much wider range of cells. This has been shown to increase the cytopathic effect and xenograft cure rate of E1B-deficient viruses (Shinoura, H., et al 1999 Cancer Res 59, 3411-3416 incorporated herein by reference).
A n alternative strategy is to incorporate the cDNA encoding for Ad40 and/or Ad4l fibres into the construct of the invention as described above. The EMBL and Genbank databases list scuh sequences and they are further described in Kidd et al Virology (1989) 172(1), 134-144; Pieniazek et al Nucleic Acids Res. (1989) November 25; 17-20, 9474; Davison et al J. Mol. Biol (1993) 234(4) 1308-16; Kidd et al Virology (1990) 179(1) p139-150; all of which are incorporated herein by reference.
In a second aspect of the invention there is provided the viral DNA construct of the invention, particularly in the form of a virus encoded thereby, for use in therapy, particularly in therapy of patients having neoplasms, eg. malignant tumours, particularly colorectal tumours and most particularly colorectal metastases. Most preferably the therapy is for liver tumours that are metastases of colorectal tumours.
In a third aspect there is provided the use of a viral DNA construct of the invention, particularly in the form of a virus encoded thereby, in the manufacture of a medicament for the treatment of neoplasms, eg. malignant tumours, particularly colorectal tumours and most particularly colorectal metastases. Most preferably the treatment is for liver tumours that are metastases of colorectal tumours.
In a fourth aspect of the invention there are provided compositions comprising the viral DNA construct of the invention, particularly in the form of a virus encoded thereby, together with a physiologically acceptable carrier. Such carrier is typically sterile and pyrogen free and thus the composition is sterile and pyrogen free with the exception of the presence of the viral construct component or its encoded virus. Typically the carrier will be a physiologically acceptable saline.
In a fifth aspect of the invention there is provided a method of manufacture of the viral DNA construct of the invention, particularly in the form of a virus encoded thereby comprising transforming a viral genomic DNA, particularly of an adenovirus, having wild type transcription factor binding sites, particularly as defined for the first aspect, controlling transcription of genes the protein products of which are directly mechanistically involved in viral nucleic acid replication, such as to operationally replace these sites by tumour specific transcription factor binding sites, particularly replacing them by Tcf transcription factor binding sites. Operational replacement may involve partial or complete deletion of the wild type site. Preferably the transformation inserts two or more, more preferably 3 or 4, Tcf-4 transcription factor binding sites. More preferably the transformation introduces additional mutations to one or more residues in the NF1, NFxcexaB, AP1 and/or ATF binding sites in the E3 promoter region of the viral genome. Such mutations should preferably eliminate interference with E2 activity by E3 and reduce expression of E2 promoter-driven genes in normal cells and non-colon cells. Reciprocally, it preferably replaces normal regulation of E3 with regulation by Tcf bound to the nearby E2 promoter.
Traditional methods for modifying adenovirus require in vivo reconstitution of the viral genome by homologous recombination, followed by multiple rounds of plaque purification. The reason for this is the difficulty of manipulating the 36kb adenovirus genome using traditional cloning techniques. Newer approaches have been developed which circumvent this problem, particularly for E1-replacement vectors. The Transgene and Vogelstein groups use gap repair in bacteria to modify the virus (Chartier et al., 1996; He et al., 1998). This requires the construction of large vectors which are specific for each region to be modified. Since these vectors are available for E1-replacement, these approaches are very attractive for construction of simple adenoviral expression vectors. Ketner developed a yeast-based system where the adenoviral genome is cloned in a YAC and modified by two step gene replacement (Ketner et al., 1994). The advantage of the YAC approach is that only very small pieces of viral DNA need ever be manipulated using conventional recombinant DNA techniques. Conveniently, a few hundred base pairs on either side of the region to be modified are provided and on one side there should be a unique restriction site, but since the plasmid is very small this is not a problem. The disadvantage of the Ketner approach is that the yield of YAC DNA is low.
The present inventors have combined the bacterial and yeast approaches. Specifically, they clone the viral genome by gap repair in a circular YAC/BAC in yeast, modify it by two step gene replacement, then transfer it to bacteria for production of large amounts of viral genomic DNA. The latter step is useful because it permits direct sequencing of the modified genome before it is converted into virus, and the efficiency of virus production is high because large amounts of genomic DNA are available. They use a BAC origin to avoid rearrangement of the viral genome in bacteria. Although this approach has more steps, it combines all of the advantages and none of the disadvantages of the pure bacterial or yeast techniques.
Although it can be used to make E1-replacement viruses, and the inventors have constructed YAC/BACs allowing cycloheximide selection of desired recombinants in the yeast excision step to simplify this task, the main strength of the approach is that it allows introduction of mutations at will throughout the viral genome. Further details of the YAC/BAC are provided by the inventors as their contribution to Gagnebin et al (1999) Gene Therapy 6, 1742-1750) which is incorporated herein by reference. :Sequential modification at multiple different sites is also possible without having to handle large DNA intermediates in vitro.
The adenovirus strain to be mutated using the method of the invention is preferably a wild type adenovirus. Conveniently adenovirus 5 (Ad 5) is used, as is available from ATCC as VR5. The viral genome is preferably completely wild type outside the regions modified by the method, but may be used to deliver tumour specific toxic heterologous genes, eg. p53 or genes encoding prodrug-activating enzymes such as thymidine kinase which allows cell destruction by ganciclovir. However, the method is also conveniently applied using viral genomic DNA from adenovirus types with improved tissue tropisms (eg. Ad40 and Ad41).
In a sixth aspect of the present invention there is provided a method for treating a patient suffering from neoplasms wherein a viral DNA construct of the invention, particularly in the form of a virus encoded thereby, is caused to infect tissues of the patient, including or restricted to those of the neoplasm, and allowed to replicate such that neoplasm cells are caused to be killed.
The present invention further attempts to improve current intra-arterial hepatic chemotherapy by prior administration of a colon-targeting replicating adenovirus. DNA damaging and antimetabolic chemotherapy is known to sensitise tumour cells to another replicating adenovirus in animal models (Heise et al., 1997). For example, during the first cycle the present recombinant adenovirus can be administered alone, in order to determine toxicity and safety. For the second and subsequent cycles recombinant adenovirus can be administered with concomitant chemotherapy. Safety and efficacy is preferably evaluated and then compared to the first cycle response, the patient acting as his or her own control.
Route of administration may vary according to the patients needs and may be by any of the routes described for similar viruses such as described in U.S. Pat. No. 5,698,443 column 6, incorporated herein by reference. Suitable doses for replicating viruses of the invention are in theory capable of being very low. For example they may be of the order of from 102 to 1013, more preferably 104 to 1011, with multiplicities of infection generally in the range 0.001 to 100.
For treatment a hepatic artery catheter, eg a port-a-cath, is preferably implanted. This procedure is well established, and hepatic catheters are regularly placed for local hepatic chemotherapy for ocular melanoma and colon cancer patients. A baseline biopsy may be taken during surgery.
A typical therapy regime might comprise the following:
Cycle 1: adenovirus construct administration diluted in 100 ml saline through the hepatic artery catheter, on days 1, 2 and 3.
Cycle 2 (day 29): adenovirus construct administration on days 1, 2, and 3 with concomitant administration of FUDR 0.3 mg/kg/d as continuous infusion for 14 days, via a standard portable infusion pump (e.g. Pharmacia or Melody), repeated every 4 weeks.
Toxicity of viral agent, and thus suitable dose, may be determined by Standard phase I dose escalation of the viral inoculum in a cohort of three patients. If grade III/IV toxicity occurs in one patient, enrolment is continued at the current dose level for a total of six patients. Grade III/V toxicity in xe2x89xa750% of the patients determines dose limiting toxicity (DLT), and the dose level below is considered the maximally tolerated dose (MTD) and may be further explored in phase II trials.
It will be realised that GMP grade virus is used where regulatory approval is required.
It will be realised by those skilled in the art that the administration of therapeutic adenoviruses may be accompanied by inflammation and or other adverse immunological event which can be associated with eg. cytokine release. Some viruses according to the invention may also provoke this, particularly if E1B activity is not attenuated. It will further be realised that such viruses may have advantageous anti-tumour activity over at least some of those lacking this adverse effect. In this event it is appropriate that an immuno-suppressive, anti-inflammatory or otherwise anti-cytokine medication is administered in conjunction with the virus, eg, pre-, post- or during viral adminstration. Typical of such medicaments are steroids, eg, prednisolone or dexamethasone, or anti-TNF agents such as anti-TNF antibodies or soluble TNF receptor, with suitable dosage regimes being similar to those used in autoimmune therapies. For example, see doses of steroid given for treating rheumatoid arthritis (see WO93/07899) or multiple sclerosis (WO93/10817), both of which in so far as they have US equivalent applications are incorporated herein by reference.
The present invention will now be described by way of illustration only by reference to the following non-limiting Sequences, Figures and Examples. Further embodiments falling within the scope of the claims will occur to those skilled in the art in the light of these.
Sequence Listing
SEQ ID No 1 is the DNA sequence of Ad 5 with the E2 and E3 transcription site mutated in accordance with the invention as shown in FIG. 2 with 4xTcf inserted in place of wild type E2 promoter.
SEQ ID No 2 is the partial amino acid sequence of the 33k protein encoded in SEQ ID No 1 unaffected by the insertion of Tcf instead of the wild type E2 promoter.
SEQ ID No 3 is the partial amino acid sequence of the pVIII protein encoded in SEQ ID No 1 unaffected by the insertion of Tcf instead of the wild type promoter.
SEQ ID No 4 is of wild type Adenovirus VR5 in the E2/E3 region.
SEQ ID No 5 is the DNA sequence of E2 late promoter as changed in a preferred virus of the invention as shown in FIG. 4.
SEQ ID No 6 is a partial amino acid sequence 100k protein encoded in SEQ ID No 5 that is unaffected by the mutations in the late promoter.
SEQ ID No 7 is the DNA sequence of E1B promoter as mutated in a preferred virus of the invention as shown in FIG. 20.
SEQ ID No 8 is that of a part of the telomerase promoter site that may be used in place of the Tcf sites exemplified herein.
SEQ ID No 9 to 25 are of primers G61 to G101 set out in the experimental herein.
SEQ ID No 26 is that of a single Tcf binding site.
SEQ ID No 27 is that of 2 Tcf sites and flanking adenoviral DNA as found in a preferred virus described herein.
SEQ ID No 28 is that of a mutant 3 Tcf site sequence with flanking viral DNA and an inactive Tcf site.
SEQ ID No 29 is that of a mutant 4 Tcf site sequence with flanking viral DNA as used in preferred viruses of the invention.
SEQ ID No 30 and 31 are forward and reverse primers for mutating the E1B promoter in a preferred virus of the invention.
SEQ ID No 32, 33 and 34 are forward and reverse primers and a probe respectively for quantitative PCR measurement of E2 expression in Taqman protocol.
SEQ ID No 35, 36 and 37 are forward and reverse primers and a probe respectively for quantitative PCR measurement of E3 expression in Taqman protocol.
SEQ ID No 38, 39 and 40 are forward and reverse primers and a probe respectively for quantitative PCR measurement of E1B expression in Taqman protocol.
SEQ ID No 41, 42 and 43 are forward and reverse primers and a probe respectively for quantitative PCR measurement of E4 expression in Taqman protocol.
SEQ ID No 44 and 45 are forward and reverse primers for fibre expression measurement.
Sequences are also provided in the Example and figures below showing primers and end construct virus sequences and their features of interest.
FIG. 1 shows wild type E2 region position where transcription factor sites are inserted in preferred adenoviruses of the invention (SEQ ID NO:46).
FIG. 2 shows E3 region changes to wild type virus in a preferred virus (SEQ ID NO:47).
FIG. 3 shows E2/E3 region of wild type virus (SEQ ID NO:4).
FIG. 4 shows E2 late promoter changes to wild type in a further preferred virus (SEQ ID NO:5).
FIG. 5 shows a diagrammatic representation illustrating steps taken in production of viruses of the invention.
FIG. 6 is a diagrammatic representation of plasmid pNxcexaBAC39.
FIG. 7 is a diagrammatic representation of plasmid p680.
FIG. 8 is a slot blot of virus infected cells probed with adenovirus DNA (A) or human genomic DNA (loading control B).
FIG. 9 is a graphic representation of results of quantatative PCR of viral DNA from virus infected cells.
FIG. 10 is a histogram showing E2 early expression in SW 480 and H1299 cell lines infected with wild type Ad5, and vMB12, vMB13 and vMB14 of the invention as measured by Taqman RT-PCR.
FIG. 11 is a histogram showing E3 expression in SW480 and H1299 cell lines infected with wild type Ad5, and vMB12, vMB13 and vMB14 of the invention as measured by Taqman RT-PCR.
FIG. 12 is a histogram showing DNA replication of wild type Ad5, and vMB12, vMB13 and vMB14 of the invention in SW480 and H1299 cell lines as measured by Taqman RT-PCR.
FIG. 13 is a histogram showing burst size (arbitrary units) with wild type Ad5, and vMB12, vMB13 and vMB14 of the invention in SW480, H1299 and W138 (fibroblast) cell lines.
FIG. 14 is a graph showing CPE results % v particles/cell of wild type Ad5, and vMB12, vMB13 and vMB14 of the invention in SW480
FIG. 15 is a graph showing CPE results % v particles/cell of wild type Ad5, and vMB12, vMB13 and vMB14 of the invention in H1299.
FIG. 16 is a plot of tumour volume v days after adminstration of buffer, vMB12, vMB13 and vMB14 in Co115 xenografts.
FIG. 17 is a histogram showing E1B-55k expression in SW480 and H1299 cell lines infected with wt Ad5, vMB14 and vMB19 of the invention.
FIGS. 18, 19 and 20 are histograms of E2 and E3 early expression and DNA replication respectively in SW480 and H1299 cells.
FIG. 21 is that of EIB promoter (SEQ ID NO:7) changes as compared to Ad5 (SEQ ID NO:48) in a preferred construct or virus of the invention.